Tobacco smoke filter

ABSTRACT

An improved tobacco smoke filter material for removing HCN from tobacco smoke is provided which comprises activated carbon impregnated with an effective quantity of cuprous chloride.

United States Patent Urbanic June 17, 1975 [54] TOBACCO SMOKE FILTER3,426,763 2/1969 Sioan et a1. 131/266 3,460,543 8/1969 Keith et a1.131/266 X [75] wanton Emery Urban, Plttsburgh, 3,724,469 4/1973 Reynoldset a1. 131/266 [73] Assignee: Calgon Corporation, Pittsburgh, Pa.Primary Examiner Me]vin Rein [22] Filed: Dec. 21, 1973 Attorney, Agent,or Firm-H. E. Westlake, Jr.; Frank h R F.

[21] App]. No.: 427,201 Ma aymond speer [52] US. Cl 131/267; 131/10.9[57] ABSTRACT [51] Int. Cl A24b 15/02 58 Field of Search 131/10-10.9, Animproved tobacco Smoke filter material for remov- 131/261-269, 17 ingHCN from tobacco smoke is provided which comprises activated carbonimpregnated with an effective [56] References Ci d quantity of cuprouschloride.

UNITED STATES PATENTS 7/1962 Schur 131/10.9

5 Claims, No Drawings TOBACCO SMOKE FILTER This invention relates to anew tobacco smoke filter material useful for the removal of noxious andirritative material from tobacco smoke. More particularly, the instantinvention is concerned with an improved tobacco smoke filter materialcomprising activated carbon impregnated with cuprous chloride; withmethods for the preparation of such filter material; and with the use ofsuch filter material for the removal of HCN from tobacco smoke.

As is well-known, constituents present in tobacco smoke formed duringthe act of smoking cigarettes, cigars, pipes and the like comprisecombustion products derived from the tobacco and consist generally ofagaseous phase in which is carried suspended liquid droplets and/or solidparticles. Many of the chemical components of the gaseous phase and ofthe liquid droplets and solid particles are believed to be harmful tothe health of the smoker and there have been proposed a variety offiltering elements to be used to clarify tobacco smoke and to removefrom it components believed to be harmful.

Amoung the many materials proposed as cigarette filter materials arevarious cellulosic materials including cellulose, cellulose acetate,cotton, paper, starch, viscose rayon and the like. These materials havebeen fabricated into a variety of smoke-filtering elements designed foruse with cigarettes, cigars and pipes either alone or in combinationwith a variety of adsorbants such as silica-gel, ion exchange resins,alumina, activated carbon and natural and synthetic clays. None of thecommercially available filter materials, however, have proved entirelysatisfactory.

Filter elements formed into cylinderical rings from cellulosic fibershave been found to be effective in removing from tobacco smoke asignificant proportion of the liquid droplets and solid particlesnormally contained therein. Such filters, however, are relativelyineffective in removing gaseous components, and notably HCN, fromtobacco smoke. Attempts to improve the gas adsorbing properties of suchfilters by incorporation therein of adsorbing materials such as thosementioned above, while showing some improvement, have been onlypartially effective in removing gaseous phase contaminants such as HCNdue to a variety of factors including partial saturation or deactivationof adsorbant during manufacture of the filter element and in subsequenthandling during the cigarette manufacturing process.

More recently, tobacco smoke filtering materials have been proposedwhich comprise gas adsorbant materials of high surface area such asactivated charcoal, alumina, natural and synthetic clays and silica-gelwhich have been impregnated with a mixture of the oxides of iron andzinc. These tobacco smoke filtering materials have been found to beeffective in the removal of gaseous contaminants including HCN fromtobacco smoke (see Keith et al., US. Pat. No. 3,251365). The instantinvention is concerned with applicants discovery that tobacco smokefiltering materials which are highly effective in removing HCN fromtobacco smoke may be prepared by impregnating granular activated carbonwith an effective quantity of cuprous chloride.

In its composition aspect, therefore, the instant invention may bedescribed as residing in the concept of a tobacco smoke filteringmaterial comprising graunlar activated carbon impregnated with cuprouschloride. It is contemplated that such tobacco smoke filtering materialwill be incorporated into cigarette filters or into cigarette and/orcigar holders or into pipe stem filter elements for the removal of HCNfrom tobacco smoke.

The instant invention is based upon applicants discovery that activatedcarbon containing from 0.5 to 15 per cent by weight is highly effectivein removing HCN from tobacco smoke. This result has been confirmed byactual test employing standard laboratory techniques. A typicalexperiment is described below.

Activated carbon containing 2.0 per cent by weight cuprous chloride wasprepared by the method hereinafter described and was loaded into mmstandard cigarettes with 20 mm filter cavities between two celluloseacetate filter plugs. Approximately mg. of impregnated activated carbonwas loaded into each cigarette to provide a filter length of about 4 mm.of carbon.

This carbon filter cigarette type was smoked and the smoke was analyzedfor HCN content. A control cigerette without an activated carbon filterand a cigarette containing the same activated carbon filter but withoutthe cuprous chloride impregnant also was smoke and the smoke from thesecigarettes was analyzed for HCN content using the same techniques.

Samples of the three test cigarettes were smoked on an automatic smokingapparatus. The smoke was drawn by syringe from the cigarette through aglass fiber filter disc and through 75 ml. of 2 percent aqueous sodiumhydroxide solution in a 100 ml. graduated cylinder. The cylinder wasfitted with a constricted tip, dip tube to provide good gas liquidcontact. A two second 40 mm. puff was taken at 58 second intervals.After the cigarette was smoked to a 35 mm. butt length, which usuallyrequired seven to nine puffs, smoking was stopped and the adsorbingsolution was removed, diluted to 100 ml. with additional 2 percentsodium hydroxide, and an approximate aliquot taken for HNC analysis.

The cyanide content of the sodium hydroxide solutions obtained above wasmeasured by a modification of the pyridine/pyrazolone procedure ofEpstein (Analytical Chemistry, Vol. 19, No. 4, 272-4, 1947). The methodis a colorimetric procedure in which the cyanide is converted tocyanogen chloride with chloramine-T reagent (sodium p-toluenesulfonchloramide). The cyanogen chloride reacts with pyridine to formglutaconic aldehyde which combines with l-phenyl-3- methyl-S-pyrazoloneto form a blue colored complex. The test procedure is described below.

The pH of the aliquot was adjusted to 7 with dilute acetic acid andtransferred quantitatively to a 50 ml. volumetrical flask. A 0.2 ml.volume of 1 percent aqueous chloramine-T. was added. The solution wasallowed to stand for 2 minutes and 5 ml. of pyridinepyrazolone solutionwas added. The contents of the flask were diluted to 50 ml. withdistilled water and allowed to stand for 20 minutes for colordevelopment. Absorbance was measured using a Beckman DK-2Spectrophotometer equipped with a lead sulfide detector. Distilled waterwas used as a reference. A graph of absorbance vs. hydrogen cyanideconcentration was prepared using solutions of 2 percent aqueous sodiumhydroxide containing known concentrations of potassium cyanide.

The results obtained are shown below:

TABLE 1 C uC l lm pregnuted C arbon Delivered per Cigarette As confirmedabove, the cuprous chloride inpregnated activated carbon filter was farsuperior to the filter containing no carbon and to the umimpregnatedcarbon filter delivering by far the lowest amount of HCN per cigaretteto the smoke passed through the filter.

The activated carbon useful in preparing the tobacco smoke filtermaterials of this invention desirably are granular activated carbonshaving mesh sizes between 4 and 40 mesh (U.S. Sieve Series).Particularly desirable are activated carbons of 12 to 40 mesh. Suchactivated carbons can have widely varying surface areas. It has beenfound that activated carbon base materials can have surface areasbetween 250 m. /g. to 1200 mf/g. with no significant change ineffectiveness. As noted above, the cuprous chloride impregnant iseffective for HCN removal from tobacco smoke in the range of 0.5 topercent by weight of the activated carbon. Increases in the impregnantlevel does not proportionally increase the removal of HCN. Filterlengths between about 2 mm. and 6 mm. are effective with 4 to 6 mm.being preferred.

The tobacco smoke filter materials of this invention conveniently areprepared by soaking the activated carbon, either before or afterscreening to the desired mesh size, in an aqueous solution of cuprouschloride and ammonium hydroxide. The activated carbon is allowed toremain in contact with the impregnating solution, either with or withoutstirring, until it has become thoroughly saturated. Usually about 1 toabout 4 hours is satisfactory. The wetted activated carbon is thenseparated from the impregnating solution and dried at about 100 to 150Cto drive off excess water and ammonia and to deposit the cuprouschloride impregnant in the activated carbon. Such drying operationusually requires about 3 to 12 hours. The amount of cuprous chloride inthe impregnating solution is selected so as to afford the proportion ofcuprous chloride which it is desired to deposit upon the activatedcarbon.

In a typical preparation, 100 g. of 18 X 20 mesh activated carbon isdeposited in a glass beaker. A solution of 2 g. of cupours chloride in50 ml. of ammonium hydroxide is prepared and diluted to 100 ml. withdistilled water. The weighed activated carbon is then stirred into thecuprous chloride solution and stirred occassionally for 3 hours. Thewetted carbon is then separated from the impregnating solution and driedover night at 100C. The cuprous chloride impregnated carbon so producedthen may be employed as the tobacco smoke filtering material inaccordance with the instant invention.

The subject matter which applicant regards as his invention isparticularly pointed out and distinctly claimed as follow:

1. The method of removing HCN from tobacco smoke which comprisescontacting said tobacco smoke with a tobacco smoke filtering materialcomprising at least about 50 milligrams of granular activated carbonimpregnated with 0.5 to 15 percent by weight of cuprous chloride. w

2. The method of claim 1 wherein said granular acti' vated carbon has amesh size between 4 and 40 mesh and is impregnated with 0.5 to 15percent by weight of cuprous chloride.

3. A smoking article having a burnable tobacco charge, a mouth end and afilter element interposed between said burnable tobacco charge and saidmouth end, said filter elememt containing a tobacco smoke filteringmaterial capable of removing HCN from tobacco smoke comprising at leastabout milligrams of granular activated carbon impregnated with 0.5 15

weight of cuprous chloride.

1. THE METHOD OF REMOVING HCN FROM TOBACCO SMOKE WHICH COMPRISESCONTACTING SAID TOBACCO SMOKE WITH A TOBACCO SMOKE FILTERING MATERIALCOMPRISING AT LEAST ABOUT 50 MILLIGRAMS OF GRANULAR ACTIVATED CARBONIMPREGNATED WITH 0.5 TO 15 PERCENT BY WEIGHT OF CUPROUS CHLORIDE.
 2. Themethod of claim 1 wherein said granular activated carbon has a mesh sizebetween 4 and 40 mesh and is impregnated with 0.5 to 15 percent byweight of cuprous chloride.
 3. A smoking article having a burnabletobacco charge, a mouth end and a filter element interposed between saidburnable tobacco charge and said mouth end, said filter elememtcontaining a tobacco smoke filtering material capable of removing HCNfrom tobacco smoke comprising at least about 50 milligrams of granularactivated carbon impregnated with 0.5 - 15 percent by weight of cuprouschloride.
 4. The smoking article of claim 3 wherein said smoking articleis a cigarette.
 5. The smoking article of claim 4 wherein said granularactivated carbon has a mesh size between 4 and 40 mesh and isimpregnated with 0.5 to 15 percent by weight of cuprous chloride.